The present invention relates to a calibration method for use in a head loading/unloading type disk apparatus and, more particularly, to a calibration method suited to automatic adjustment of the velocity detection value used in unloading.
Recently, some disk apparatuses for recording and reproducing information by using a head, e.g., some small magnetic disk apparatuses use a head retraction method called a loading/unloading method. The characteristic feature of this loading/unloading method is as follows. When no data read/write operation is performed, e.g., when the rotation of a disk (recording media) is stopped, a head stops on a ramp mechanism positioned outside the outer periphery of the disk. In this state, the head is moved from a retraction position on the ramp mechanism onto the disk by an instruction from a host to thereby perform a read/write operation. When the read/write operation is complete, the head is returned from the disk onto the ramp mechanism.
The operation of moving the head from the ramp mechanism onto the disk is called loading, and the operation of moving the head from the disk onto the ramp mechanism is called unloading.
Jpn. Pat. Appln. KOKAI Publication No. 8-63920 has disclosed an apparatus for loading and unloading an arm having a head slider to and from a rotary information recording disk by driving the arm by an actuator. In this apparatus, the back electromotive force of a voice coil type driving mechanism of the actuator is detected and fed back to a driving control circuit, and this control circuit controls the position and velocity of the actuator. That is, this reference describes that when loading or unloading is performed, velocity feedback control is performed by detecting the VCM velocity by using the back electromotive force generated in the voice coil motor (VCM).
In this prior art, however, which performs velocity feedback control by detecting the VCM velocity by using the back electromotive force generated in the voice coil motor (VCM), if the resistance of the coil of the VCM changes due to temperature change or the like, the relationship between the value (VCM current value) of current flowing through the VCM and the VCM velocity detection value also changes. This makes accurate velocity feedback control impossible to perform. The above reference does not describe the nature of the problem and a method of solving the problem when the resistance of the coil of the VCM changes due to temperature change or the like and the relationship between the VCM current value and the VCM velocity detection value changes.